Amine-modified epoxy resin reacted in presence of latent hardener

ABSTRACT

A method for making a one component heat curable epoxy resin system by mixing together (A) an epoxy resin or compound containing more than one epoxy group; (B) an amine solidifying system present in insufficient quantities to cause gelation after the amino hydrogen atoms are consumed by epoxy groups, under the reaction conditions chosen for (A) and (B); (C) a hardener system for (A) and the reaction product of (A) and (B), wherein (C) is different from (B); and (E) an expanding agent, wherein (A) and (B) react to completion at room temperature in the presence of (C) and (E), and wherein the reaction between (A) and (B) does not cause (C) or (E) to substantially react.

[0001] Hot melt one component thremosettable epoxy resin compositionsare difficult and hazardous to manufacture and pack. These difficultiesoften give rise to variability in the product both from batch to batch,container to container and even within containers.

[0002] These problems arise because the compositions contain viscous orsolid resins as well as hardeners and are mixed in the hot viscousmolten state. This can result in the reaction fully or partiallyoccurring during mixing, discharging, or even in the end container.

[0003] This invention relates to methods utilising a specific type ofcomposition for the safe and consistent manufacture and where requiredthe simple filling of end use containers of one component heat curable,solvent free, hot melt epoxy resin compositions which have a meltingpoint less than 55° C.

[0004] Because of safety, cost and possible environmental pollution itis becoming increasingly important to avoid the use of volatile solventsin industrial processes. Because of the need to maintain a safe, cleanand healthy workplace, as well as manufacturing convenience, contactwith all liquid chemicals should be avoided wherever possible.

[0005] These needs favour the use of epoxy resin formulations in solventfree, flexible or solid form and account in part for the increasingpopularity of preimpregnated fibres, or prepregs, for the manufacture ofreinforced composites, adhesives in hot melt and flexible tape form forbonding and the use of powders for coatings.

[0006] It is very important that the physical nature of these epoxyformulations is very consistent during storage because this affects theability to apply them reliably and produce consistent quality items withthem.

[0007] Mixing of the epoxy formulation does not present manufacturingproblems is made in solution, as the ingredients can be mixed at lowtemperatures to avoid dangerous reaction between the resins andhardeners present, due to the low mix viscosities achieved by the use ofsolvents, but the manufacture and packaging of solvent free individualbatches of reactive hot melt epoxy resin and hardener is much moredifficult and dangerous, especially when the final composition isrequired to cure at temperatures say up to 180° C., due to the risk ofthe curing reaction being initiated prematurely.

[0008] Alternatively, mixing of the ingredients can be carried outcontinuously, which usually avoids the danger of major heat or reactionbeing given out in the blending equipment, even if carried out atelevated temperatures because only small quantities are present in themixer at any one time. But the danger remains of reaction in thecontainers the mixture is poured into.

[0009] The result of reaction may be very serious where it proceeds outof control, leading to large quantities of decomposition gases, burntproducts, damaged equipment and harzards to personnel, the workplace andthe environment in general. Where the reaction only partly proceeds itleads to an increase of average molecular weight, either in the wholebatch, or variably within a batch, or a container, for example as theresult of different heating times coming from the variation in run-outtimes from the mixing vessel or cooling within a container. Any suchpartial reaction is very bad as it results in changed application anduncured physical properties either of the whole batch or container or,more likely, variability within it.

[0010] Because of these difficulties the volumes of many hot melt epoxycompositions that can safely be mixed at one time or be put hot into acompact bulk in a container rarely exceed 100 liters. Where the finalcomposition is required to cure at 130° C. or below even 25 liter mixesare potentially dangerous.

[0011] Whether mixed continuously or batchwise the filling of smallcontainers with hot viscous reactive liquids present major problems,particularly so when the viscosities at the permitted fillingtemperatures are high.

[0012] So a new method was needed to manufacture these difficult andhazardous materials both safely and in reproducible quality, includingtheir presentation in practical end use containers.

[0013] We have now discovered a surprisingly simple way to make theseone component epoxy hot melts consistently and safely and supply them ina wide variety of containers and shapes suitable for later hot melt orother processing applications. This process uses very mild conditionsand consists of making an epoxy formulation which is liquid at 80° C. orbelow, more usually at normal shop floor temperatures (15° C.-30° C.)and adding to it a chemical solidifying system which reacts very slowlyat these temperatures with the epoxy materials present.

[0014] The solidifying system must be picked to give very littlereaction during the time it is being mixed with the epoxy resin andhardeners, by whatever method this is done, so that there is very littleviscosity rise or temperature rise during the blending operation andhence making the filling of large or small, simple or complicatedcontainers a relatively easy task. Alternatively mixing may take placein the final container if required.

[0015] The solidifying reaction must be a simple amine addition reactionwith the epoxy groups and must stop when the addition reaction stops. Notertiary amines may be present in the initial mixture or generatedduring the reaction which could significantly react under the conditionschosen for the solidification reaction. Such reactions severelycompromise, safety during bulk mixing, the state of solidification oncemixed and the melting point stability and shelf life of the resultantproduct. The solidifying system must be picked to satisfy thesecriteria.

[0016] The levels of solidifying system used have a major effect on thephysical nature of the fully reacted, uncured product. With a liquidresin increasing amounts of solidifying systems take the product throughthe stages of high viscosity, high tack, low tack, zero tack,flexibility and brittleness respectively.

[0017] For convenience, most of the solidification reaction should takeplace in the final containers used to receive the mixture and thisshould take place slowly enough to ensure that, in the selected size andshape of the container, there is no temperature rise high enough tocause any significant reaction between the epoxy resins and their maincuring systems, but fast enough to ensure usability in a sensible time.

[0018] The solidifying agent may be introduced into the mixture at anystage in the process provided the reaction basically proceeds as above.

[0019] As the necessary quantity of the solidification system reacts theviscosity and melting point of the formulation increases until thereaction approaches completion when the physical nature of the finalformulation is close to the desired end use requirements.

[0020] The present invention provides for the manufacture of onecomponent hot meltable thermosettable epoxy resin formulations in bulkform in batch or continuous mixes and their presentation in containersintended for further processing by melt, or other, application methodsand includes their composition in hot meltable, molten, powdered, solid,semi solid, tacky, bulk and final cured forms. For example the method ofthis invention could be performed using the following classes ofingredients:

[0021] (A) epoxy resins or epoxy containing compounds

[0022] (B) a solidifying amine system which will react with (A) to givea product with a Kofler Heat Bank melting point of less than 55° C., butwhich is not present in sufficient quantities to allow or cause chemicalgelation under the reaction conditions chosen for (A) and (B) and whichessentially stops solidifying once its active epoxy additive hydrogengroups are consumed by the epoxy groups, optionally

[0023] (C) a hardener system for (A) and the reaction product of (A) and(B) which is different from (B) and which remains substantiallyunreacted under the conditions of reaction chosen for (A) and (B) with(A) and (B), optionally

[0024] (D) other additives that may be required to modify the physicalproperties of the cured or uncured composition, and optionally (E) anexpanding agent.

[0025] The method is carried out by blending (A), (B), and optionally(C), (D) and (E) together by any convenient batch or continuousoperation but in such a way that at least (A) and (B) becomehomogeneous. The reaction between (A) and (B) may be carried out at anysuitable temperature and condition provided that neither it, nor theexothermic heat generated from it causes (C) or (E) to substantiallyreact whilst it is taking place.

[0026] The epoxy resins or epoxy group containing compounds, (A)employed in this invention may be glycidyl ethers, glycidyl amines,glycidyl esters or cycloaliphatic compounds, or combinations of theseincluding halogenated versions where required. Preferred epoxy resinsand blends are those which are suitable liquids for ready mixing withthe other ingredients at suitable temperatures which will usually bebelow 100° C. Epoxy resins or epoxy containing compounds or blends ofthem which are liquid at room temperatures are the most convenient.

[0027] The preferred solidifying systems (B) used to convert the liquidresins are principally compounds or mixtures of compounds whose mostreactive groups relative to the epoxy materials employed are primary orsecondary amines. Epoxy reactive tertiary amines under the conditions ofreaction chosen for (A) and (B) are not acceptable for this invention.

[0028] Of particular usefulness in this process are aromatic andcycloaliphatic primary and secondary amines and blends of these. Themajor advantage of these amines, particularly the aromatic amines, isthe low rate of reactivity coupled with the extremely long life atnormal ambient temperatures of their reaction products with the resins.With the majority of compounds from these clasess of amines the life orthe reaction product with the resins greatly exceeds that of the life ofthe resins with their primary hardeners (C). Some alicyclic,heterocyclic and aliphatic amines are also effective as advancing agentsand those which comply with virtual cessation of reaction once theiramino hydrogen atoms have been consumed by the epoxy resins areconsidered as part of this invention. In all cases it is essential thatthe tertiary amines generated during the solidification reaction havevery low reactivity with epoxy groups under the conditions of reactionchosen for (A) and (B) and afterwards during storage. The solidifyingamines are usually and mostly difunctional and/or polyfunctional withrespect to the epoxy compounds, (A), although monofunctional amines canbe used to some extent if of value to a particular composition.

[0029] Difunctional amines may be used at any desired ratio withdifunctional epoxy resins but greater than difunctional amines only tolevels where gelation does not occur. The solidifying systems maycontain a variety of other groups but these should only be of very lowor no reactivity towards the epoxy groups involved under the reaction of(A) with (B).

[0030] The hardener systems (C) for the epoxy compounds (A) and thereaction products between (A) and (B) can be selected from the widevariety of those well known in the field of epoxy chemistry other thanacid anhydrides which react preferentially with the advancing agents(B). Typical but not exclusive examples of useful hardeners are aromaticamines such as diaminodiphenyl sulphones, boron trifluoride aminecomplexes, latent imidaxoles, carboxylic acids, hydrazides,dicyandiamide, latent epoxy amine adducts and substituted ureas. Asexplained a main requirement of the hardener is that it should notsubstantially react whilst (A) and (B) are being reacted to form theepoxy composition which has a melting point less than 120° C. There maybe one or several hardeners used together, some of which may acceleratethe curing rates of the others provided they comply with the requirementimmediately above.

[0031] Other additives (D) which can be used to modify the physicalproperties of the cured or uncured compositions include but are notlimited to thixotropes, toughening agents, wetting agents, surfactants,fibrous materials, dyes, pigments, fillers, flame retardants, smokesuppressants, coupling agents, hollow microspheres, flow assistingmaterials, fusible glasses, expanding agents and stabilisers.

[0032] Suitable expanding agents are those which generate gases bychemical decomposition or by boiling of liquids or expansion of gasescontained within exandable shells.

[0033] Examples of suitable expanding agents include

[0034] Azodicarbonamide, Azodiisobutyronitrile, Benzenesulphonhydrazide, Dinitroso pentamethylene tetramine, Oxybis benzenesulphonhydrazide, p toluene sulphonyl hydrazide and Expandable plasticsuch as those sold under the Trade Name Expancel. These are largelyspherical shells of varying composition such as polyvinylidene chlorideand or polyacrylonitrile plus other copolymerised additives, and theinside contains isopentane ±air.

[0035] It will be clear to those familiar with epoxy resins that theactual mixing and storage temperatures, the geometry and volume of themixing vessel and the containers the mixing and filling times requiredas well as the actual resins and the quantity of them used will allinfluence the selection of the solidifying agents. It would not be goodfor instance to choose a solidifying agent which reacts to generatesubstantial heat during the mixing operation or in the selectedcontainer shape and size. Thus the less reactive amines are the mostsuitable solidifying agents for practical batches and containers whereasmost aliphatic amines are unsuitable alone, because they are highlyreactive.

[0036] Most useful are those solidifying systems which react graduallyto substantial completion at room temperatures over a period of around2-14 days. These permit the safe manufacture of batches in excess of 100liters in a realistic mixing time with little temperature rise in themixing vessel or during discharge and smooth reaction to the requiredphysical state in most practical containers, however mixed, over apractical timescale. Under these conditions the heat of reactiongenerated by the soldification process is evenly dissipated byconduction and radiation and results in no more than acceptabletemperature rises at any stage in the process.

[0037] The primary controlling factor being that the mixture reactiontemperature rise whether in the mixing vessel or the containers shall bebelow that required to cause significant reaction between (A) and (C).

[0038] Should it be desirable to speed the solidification in the finalcontainer this can be achieved by heating, provided the temperature useddoes not cause significant reaction of (C) with (A) or the reactionproduct of (A) with (B) either by direct heat or that evolved bycompleting the reaction between (A) and (B), or by the addition ofaccelerators such as carboxylic acids, which do not adversely affect thesoftening point stability.

[0039] The solidifying systems must be present in such quantities thatwhen their amino hydrogen atoms are all substantially reacted with theepoxy materials (A) under the conditions set for reacting (A) and (B)the product is not chemically gelled and has a melting point which isessentially stable for greater than 6 months at 22° C.

[0040] The selection and quantity of the solidifying agent will alsoinfluence a variety of properties such as melt viscosity, stength,toughness and heat resistance and by careful choice advantages may bedesigned into the uncured or cured products resulting from the use ofthis process.

[0041] Examples of this invention are as follows and particularlyillustrate the effects of solidifying systems. Where no hardener (C) isquoted it is clear that such a material can be added in a practicalproduct if required. Such examples shows that the process of advancingthe epoxy resins use is in full accordance with this invention and dogive the shelf life stability of at least six months which is anintegral advantage of this invention.

EXAMPLE 1

[0042] The following mixture was made in a blade mixer:

[0043] Liquid Bisphenol A epoxy resin (EPIKOTE 828-SHELL CHEMICAL CO)(epoxy value 5.3 equivalents per kilogram) 100 kilograms

[0044] Solidifying agent Hardener 932 (ex CIBA-GEIGY)- a blend ofaromatic amines 6 kilograms

[0045] The initial temperature of the ingredients was 26° C.

[0046] After mixing for 30 minutes it was discharged into drums—at thattime the mix temperature was 26.5° C.

[0047] A standard 25 kg drum of this mixture was monitored fortemperature rise in a room temperature of 22° C.

[0048] The maximum temperature recorded of the reacting mixture was27.6° C. which was reached 5 hours 30 minutes after the start of mixing.

[0049] After seven days at 22° C. the resulting solidified resin was atacky solid which when hot melted onto a polythene sheet gave a tackyflexible film suitable in nature for making prepregs or adhesive tapes.

[0050] After 14 days at 22° C. the mixture was still tacky and flexiblebut slightly harder than after 7 days.

[0051] 1 kilogram of this 14 day old blend was then heated to 80° C. for2 hours. On cooling it differed little from the unheated materialshowing that the solidifying reaction was almost complete at 22° C. andheating at 80° C. for 2 hours had no adverse physical effect. Samples ofthe post heated and unheated solidified products were stored at roomtemperature for occasional physical assessment. No noticeable change intack or flexibility occurred for at least 9 years.

EXAMPLE 2

[0052] A similar experiment was carried out to EXAMPLE 1 in which thesolidifying agent was increased in quantity to 8 kilograms.

[0053] The maximum temperature rise recorded in a 25 kg full drum was2.2° C. that is from 26° C. to 28.2° C.

[0054] The product after 14 days storage at 22° C. was a soft solid witha low level of tack and could be ideal for tape adhesive manufacture.

[0055] Storage of unheated samples and others post heated for 2 hours at80° C. showed no obvious change in flexibility after 8 years.

EXAMPLE 3

[0056] A similar experiment was carried out to EXAMPLE 1 in which thesolidifying agent was made up as follows: Hardener 932 10.0 kilogramsAminobenzene 1.9 kilograms

[0057] This mixture was added to 100 kilograms of the Bisphenol A resinand rapidly stirred in a planetary mixer for 30 minutes.

[0058] The temperature of the starting materials was 23° C.

[0059] After mixing for 30 minutes the temperature was 26° C.

[0060] The maximum temperature reached in a 25 kg full drum was 31° C.

[0061] After 14 days this mixture was a hard, brittle solid at 22° C.which on heating to 55° C. became a flexible solid.

[0062] The mixture was cast onto release paper at 120° C. and aftercooling could easily be broken into flakes at 22° C. which only slowlystuck together at this temperature.

[0063] When applied to heated clean metal surfaces at 120° C. and thesebeing held together until cool then even without a hardener for theresins the solidified product acted as a hot melt adhesive.

EXAMPLE 4

[0064] The following mixture was made in a Z blade mixer: LiquidBisphenol A epoxy resin (I.Y556 - CIBA-GEIGY) 100 kilograms Hardener 932(ex CIBA-GEIGY) 7 kilograms Micronised dicyandiamide 5 kilograms 1phenyl 33 dimethyl urea 4 kilograms Finely divided silica thixotrope 4kilograms

[0065] All the ingredients were blended together until homogeneous andfree from lumps. This took around 40 minutes during which thetemperature of the mixture increased from 22° C. to 24° C. The contents,which were a soft runny paste, were poured into drums containing 25 kgsof mixture and the temperature of these drums measured regularly. Themaximum temperature reached was 29° C. After 14 days the contents wereheated to 50° C. and poured into a heated bath and then cast into a thinfilm on release foil. The films produced had good flexibility and tackand were easily impregnated into unidirectional carbon tape and carbonfabrics. The prepregs also had excellent tack and drape as required bythe composites industry. On heating the formulation for 1 hour at 120°C. or 4 hours at 92° C. excellent thermoset cured products were obtainedwith Tgs of 130° C. and 125° C. respectively. Prepregs were stored atroom temperature and −16° C. to test their shelf life by loss of lackand flow on heating. Storage at R. Temp. Storage at −16° C. Tack lifegreater than 6 months greater than 1 year Gel time 10-12 months greaterthan 3 years

[0066] By deduction from EXAMPLE 2 the limit on the storage life is setby the hardener system rather than the solidifying system.

EXAMPLE 5

[0067] A similar experiment was carried out to EXAMPLE 4 but 1 kilogramof accelerator DY219 (believed to be a liquid carboxylic acid exCIBA-GEIGY) was included in the mixture. During 20 minutes mixing thetemperature increased from 22° C. to 26° C. The contents were pouredinto drums containing 25 kgs and the maximum temperature recorded was34° C. After 2 days storage at 22° C. the product was a lightly tackyflexible solid suitable for the manufacture of prepregs without the needfor preheating to 50° C. as in EXAMPLE 4.

EXAMPLE 6

[0068] A mixture was made in a high speed stirrer as follows: LiquidBisphenol A resin 100.0 kilograms 33′ dimethyl 44′ diamino dicyclohexylmethane 6.5 kilograms

[0069] The starting temperature of the materials was 22° C.

[0070] After 10 minutes mixing the temperature had increased to 28° C.and the mixture was poured into metal trays containing 25 kg. Thetemperature of the mixture in the trays rose steadily to reach 44° C. in90 minutes. It then gradually cooled to a room temperature of 22° C. Theresultant solidified resin had good tack and flexibility and should beexcellent for the manufacture of prepregs.

[0071] 1 kilogram of this blend was heated for 2 hours at 80° C. andshowed no obvious change in tack or flexibility when cooled to roomtemperature.

[0072] On storage at room temperature the solidified resin showed somedecrease in tack but was still flexible after 18 months.

EXAMPLE 7

[0073] The following mixture was made in a planetary mixer: LiquidBisphenol A resin 100 kilograms 33′ dimethyl 44′ diamino dicyclohexylmethane 6 kilograms Aluminium powder 150 kilograms MicronisedDicyandiamide 6 kilograms Finely divided silica thixotrope 2 kilograms

[0074] All the ingredients were blended together for 20 minutes, duringwhich the temperature of the mix increased from 20° C. to 26° C. Thecontents were poured in 25 kg lots into lined metal trays. After 2 hoursa maximum temperature of 48° C. was reached by the resin mixes. After 14days each separat lot of 25 kilograms of the solidified resin was atacky flexible solid. Each was heated to 60° C. and cast into a tape onrelease foil. These tapes were used to bond 16 s.w.g. aluminium alloysheets together in lap shear joints. A one half inch overlap bond wasmade. The assemblies were cured under light pressure for 1 hour at 180°C. When tested in lap shear the following breaking loads were recorded:Lot 1 1,730 lbs Lot 4 1,800 lbs Lot 2 1,840 lbs Lot 5 1,780 lbs Lot 31,900 lbs

[0075] and these demonstrated the excellent reproducibility of theprocess. The tape was stored at room temperature and −16° C. to assesstack and flexibility life. The film remained tacky at room temperaturefor at least 6 months and did not lose flexibility in 12 months. At −16°C. tack life has been preserved for at least 3 years.

EXAMPLE 8

[0076] The following mixture was prepared: Liquid Bisphenol A epoxyresin (EPIKOTE 828) 10 kilograms 44′ diamino diphenyl methane 1 kilogram

[0077] The amine and two kilograms of resin were quickly warmed to meltthe solid flakes and obtain a uniformly stirred mixture. This wasimmediately added to the remaining 8 kilograms or cold resin in a Zblade mixer.

[0078] When thoroughly mixed it was poured into a drum at 24° C., themixture being at 28° C. After 14 days the mixture had become a hardbrittle solid at 23° C. This solid was easily broken into lumps onimpact and these were quickly ground into a powder. This powder easilymelted on warming and had a softening point of less than 50° C. Thepowder quickly sintered together on standing at 23° C. The material isan interesting one in its own right but is unsuitable for use in powderform if used or stored at normal shop floor temperatures.

EXAMPLE 9

[0079] The following mixture was made in a Z blade mixer: LiquidBisphenol A epoxy resin (EPIKOTE 828) 10.0 kilograms 33′ dimethyl 44′diamino dicyclohexyl methane 0.7 kilograms

[0080] When properly mixed the liquid was poured into a mould and themaximum temperature reached was 40° C. The product when cooled to 22° C.was a lightly tacky, soft flexible solid. After 14 days at 22° C. it wasa little less tacky but still a soft flexible solid. It stayed in thiscondition basically unchanged for 2 years at 22° C.

[0081] A portion of this product was heated to 60° C. for 7 days. Duringthis period it stayed at liquid at 60° C. and on cooling to 22° C. wasstill a soft solid but rather less tacky. This EXAMPLE shows theexcellent stability of the basic liquid epoxy resin and its solidifiedproduct to the tertiary amine created by reacting the epoxy resin groupswith this amine.

EXAMPLE 10

[0082] The following mix was made: GY 260 (˜5.3 epoxy/kg) 100.001,1,3,3-tetramethyl butylamine 17.3

[0083] The mixture reacted slowly at 22° C. After 18 days it was a semisolid with a melting point of approximately 30° C. After 121 days at 22°C. the composition appeared unchanged and possessed a similar meltingpoint.

[0084] A further sample of this composition, freshly prepared, produceda material of the same texture at 22° C. after heating for 23 days at60° C.

[0085] This is an example of a hindered aliphatic amine (B) which wouldbe suitable for the present invention when a latent hardener (C) wasincorporated into the composition.

EXAMPLE 11 to 13

[0086] The following mixtures were made in a planetary mixer: EXAMPLE 1112 13 Liquid Bisphenol A epoxy 100 100 100 resin-kilograms (EPIKOTE828 - SHELL CHEMICAL CO) (epoxy value 5.3 equivalents per kilogram)amino benzene-kilograms 5 8 12 They were poured into 25 kilogram drums.The initial temperature of all five mixtures was 21° C. Maximumtemperature rise 2° C. 2.2° C. 3.4° C. Texture after 14 days at 22° C.soft. tacky flexible hard slight tack brittle After 5 hours at 60° C.soft. tacky flexible hard slight tack brittle examined at 23° C. KoflerHeat Bank below below approx. Melting point ° C. 22* 22* 55 Kofler HeatBank below below approx. Melting point ° C. 22* 22* 57 after 4 yearsstorage at shop floor temperature

[0087] These examples show the wide range of texture that can beachieved in hot meltable products made using this invention.

[0088] They also show the very low exotherms that can be achieved duringmixing and solidifying which clearly show that very heat sensitivehardeners (C) can safely be added.

[0089] They also show the excellent stability achievable on shopfloorstorage which is a great advantage of this invention.

EXAMPLES 14 to 16

[0090] The following mixtures were made in a planetary mixer: EXAMPLE 1415 16 EPIKOTE 828 kilograms 10.0 10.0 10.0 amino benzene kilograms  0.5 0.8  1.2 dicyandiamide fine powder kilograms  0.8  0.7  0.5 They werepoured into 25 kilogram durms. The initial temperature was 22° C.Maximum temperature rise ° C.  2  2  3 Texture after 14 days at 22° C.soft flexible hard tacky slight tack brittle Texture after 5 hours at60° C. soft flexible hard examined at 22° C. tacky slight tack brittleKofler Heat Bank Melting point below below approx. after 14 days at 22°C. in ° C. 22* 22* 55 Texture after 6 months at shop soft flexible hardfloor temperature examined at 22° C. tacky slight tack brittle KoflerHeat Bank Melting point below below approx. after 6 months storage atshop floor temperature in ° C. 22* 22* 55 Texture after 1 year at shopflexible flexible hard floor temperature examined at 22° C. low no tackbrittle tack Kofler Heat Bank Melting point below below approx. after 1year at shop floor 30* 35* 55 temperatures in ° C. Texture after 4 yearsat shop hard hard hard floor temperatures brittle brittle brittleexamined at 22° C. Kofler Heat Bank Melting point approx. approx.approx. after 4 years storage at shop 45 47 58 floor temperatures in °C.

[0091] After 14 days at 22° C. portions of EXAMPLES 14 to 16 were coatedonto 16 s.w.g. aluminium alloy sheets which had been preheated to 120°C. Lap shear joints were produced using a width of one inch with aone-half inch overlap. The assemblies were cured under light pressurefor 1 hour at 180° C. When tested in lap shear the following averagebreaking loads were recorded: EXAMPLE 14 1,620 lbs EXAMPLE 15 1,920 lbsEXAMPLE 16 2,430 lbs

[0092] These examples show the excellent workshop stability of thisinvention.

[0093] They also show by comparison with EXAMPLES 11 to 13 that withlower melting point curable hot melt formulations the storage stabilityis controlled by the primary hardener (C) rather than the solidifyingsystem (B).

[0094] They also demonstrate the excellent shear strength propertiesachievable using materials according to the invention.

EXAMPLE 17

[0095] The following mixture was made in a planetary mixer: 17 EPIKOTE828 100 33′dimethyl 44′diamino dicyclohexylamethane  7 dicyandiamidefine powder  5 silica thixotrope fine powder  4 1 phenyl 33 dimethylurea  4 Texture after 24 hours at 22° C. soft sticky Texture after 120hours at 22° C. soft tacky Texture after 14 days at 22° C. soft tackyTexture after 6 months at 22° C. soft flexible Texture after 1 year at22° C. brittle Texture after 2 years at 22° C. gelled

EXAMPLE 18

[0096] Lap shear joints were prepared according to EXAMPLE 14 with thecomposition of EXAMPLE 17. After curing for 4 hours at 92° C. an averagebreaking load of 1.426 lbs was recorded. This demonstrates the abilityof using a composition of this invention to achieve at least six monthsflexible life at shop floor temperature together with the ability tocure at very low temperatures and achieve high shear strengths.

[0097] The products resulting from EXAMPLES 11, 12, 13, 14, 15 and 17possess tack and or flexibility at normal workshop temperatures and aregood for uses where lower temperature application is important and whereresistance to damage where applied and before curing is highest. Theproducts resulting from EXAMPLES 13 and 16 are completely dry and can beused for adherring materials together before final curing and forstorage of parts without readily tacking together before final assemblyand cure. These EXAMPLES show that it is easily possible to design inthe physical uncured characteristics of the products as well as thefinal cured properties by the use of this invention.

[0098] As may be seen from the foregoing examples, this chemicalapproach to the production of curable epoxy hot melt compositionsemploys conditions much less rigorous than current standard techniqueswhich require mix temperatures of around 60-100° C. or even above.

EXAMPLE 19

[0099] A mixture was made of: GY 260 (˜5.3) 100.0 parts by weight44′diamino 33′dimethyl dicyclohexyl methane 7.0 parts by weight 3 chloro4 methyl phenyl 1,1 dimethylurea 3.5 parts by weight dicyandiamide 7.0parts by weight hydrophobic fumed silica 7.5 parts by weight ExpancelDU551 3.0 parts by weight

[0100] This non flowing paste was easily extruded (or placed) into aplastic (polypropylene) cartridge and allowed to react at 22° C.

[0101] After 24 hours it was a lightly tacky putty. The loaded cartridgethen placed in an oven for 2 hours at 50° C. On cooling it was aflexible non tacky putty.

[0102] On warming the cartridge to 60° C. the mixture became soft andcould be extruded easily through the integral nozie.

[0103] The composition was extruded onto a flat clean metalic plate in apreset pattern. On cooling the warmed material regained its putty likeconsistency and maintained its shape and adhered to the plate.

[0104] The plate was then placed in an oven at 120° C. for 60 minutes.After this time the composition had foamed and hardened and basicallyretained the initial laid down extruded pattern. The cured framedmixture showed strong adhesion to the metal plate.

[0105] It will be clear from these examples that this invention providesfor the safe and reproducible quality manufacture and isolation ofsolvent free, one component, thermosettable epoxy formulations insuitable shape and form for further hot melt or other processingapplications. These may well then be used in the casting of tapes asadhesives or for impregnation into fibres to make prepregs or generaluse as adhesives, encapsulants, electrically insulating materials andmouldings amongst others as well. They may be used in other shapes suchas rods, pellets, powders and sheets or applied as coatings or discreetspots or any other pattern for a variety of purposes as requirements forsolvent free one part epoxy resin systems grow.

[0106] With the current invention, in many cases, the epoxy resin blendsare liquid at 22° C. and the solidifying reaction takes place at thesame temperature.

[0107] If further heating is required to obtain a stable pourable powderat 22° C. or thereabouts it rarely needs to be above 50° C. -60° C.

[0108] The simplicity and mildness of the approach to making thesematerials enables the incorporation of a wider variety of heat sensitiveadditives including hardeners and accelerators than is possible with theHot Melt method and yields products with outstandingly long shop floortemperature storage times.

[0109] The use of temperatures above 60° C. to obtain suitable solids isonly necessary to increase speed or throughput in production.

1. A method for the manufacture of one component, heat curable,thermosettable, epoxy resin systems and their placement in convenientcontainer types, sizes and shapes, which comprises mixing (A) epoxyresins, or epoxy containing compounds (B) an amine solidifying systempresent in insufficient quantities to cause gelation after all the aminohydrogen atoms are consumed by epoxy groups, under the reactionconditions chosen for (A) and (B), and which yields a product with aKofler Heat Bank melting point of less than 55° C. and melting pointstability of at least six months at normal workshop temperatures,optionally (C) a hardener system for (A) and the reaction product of (A)and (B) which is different from (B) and remains substantially unreactedunder the conditions of reaction chosen for (A) and (B) with (A) and(B), optionally (D) other additives that may be required to modify thephysical properties of the cured or uncured composition and optionally(E) an expanding agent in such a way that very little reaction isallowed to take place during the mixing operation between (A) and (B)and most of it takes place in the final shape or container it is neededin before further melt or other processing, provided that the reactionbetween (A) and (B) does not generate enought heat in the chosen shapeor container to significantly activate reaction between the remainingepoxy groups and hardener (C), or expanding agent (E).
 2. A methodaccording to claim 1 in which the mixing of the composition is carriedout batchwise or continuously.
 3. A method according to claim 1 or 2where the choice of composition, mixing method, temperature and timeminimises the reaction between (A) and (B) during mixing and is too mildto significantly activate hardener (C) or expanding agent (E).
 4. Amethod according to any preceding claim where the mixed composition andthe shape and size of container ensure that the excess heat generateddoes not increase the temperature of the composition to a point tosignificantly activate hardener (C) or expanding agent (E).
 5. A methodaccording to any preceding claim where the mixed composition is put intothe required shape and size of container and allowed to react atworkshop temperatures until the required solidification level has beenreached.
 6. A method according to any preceding claim where thecomposition is mixed in its final container.
 7. A method according toany preceding claim where the solidification reaction approachescompletion between 1 and 30 days, preferably between 2 and 14 days.
 8. Amethod according to any preceding claim where the partially solidifiedcomposition is heated to speed completion provided the temperaturechosen or the temperature reached due to the completion of thesolidification reaction does not significantly activate hardener (C) orexpanding agent (E).
 9. A method according to any preceding claim wherethe majority of the epoxy groups are present as glycidyl ether, glycidylamine, glycidyl ester, cycloaliphatic and other epoxy resins.
 10. Amethod according to any preceding claims where the epoxy groupcontaining compounds individually or as mixtures are free flowingliquids at 80° C. or below.
 11. A method according to any precedingclaim where the solidifying agents are mainly aromatic cycloaliphatic ordicyclic primary amines, secondary amines or mixtures thereof andoptionally acid accelerators.
 12. A method according to any precedingclaim where the majority of the solidifying amine groups aredifunctional and polyfunctional with respect to the epoxy groups.
 13. Amethod according to any preceding claim where hardener system (C) ispresent and is selected from aromatic amines such as 44′ diaminodiphenylsulphone, boron trifluoride amine complexes, latent imidazoles,carboxylic acids, hydrazides, dicyandiamide, latent epoxy amine adductsand substituted ureas.
 14. A method according to any preceding claimwhich contains additional materials to modify the physical properties ofthe cured or uncured composition.
 15. A method according to anypreceding claim in which expanding agent (E) is present and is an agentgenerating gases by chemical decomposition or by boiling of liquids orexpansion of gases contained within expandable shells.
 16. A onecomponent, heat curable, thermosettable, epoxy resin system obtained byreacting (A) an epoxy resin or epoxy containing compounds with (B) anamine solidifying system present in insufficient quantities to causegelation after all the amino hydrogen atoms are consumed by epoxygroups, under the reaction conditions chosen for (A) and (B), and whichyields a product with a Kofler Heat Bank melting point of less than 55°C. and melting point stability of at least six months at normal workshoptemperatures, optionally in the presence of (C) a hardener system for(A) and the reaction product of (A) and (B) which is different from (B)and remains substantially unreacted under the conditions of reactionchosen for (A) and (B) with (A) and (B), optionally in the presence of(D) other additives that may be required to modify the physicalproperties of the cured or uncured composition and optionally in thepresence of (E) an expanding agent which remains substantially unreactedunder the conditions of reaction chosen for (A) and (B) with (A) and(B).
 17. A system according to claim 16 in which hardener system (C) ispresent.
 18. A system according to claim 16 or 17 in which expandingagent (E) is present.
 19. The use of a system according to any one ofclaims 16 to 18 for processing by hot melt techniques.
 20. A curedproduct obtained by heating a system according to any one of claims 16to 18.